The present invention is generally directed to a fluid rotary union (FRU) and, more specifically, an FRU that is designed to operate in a relatively effective manner.
There are numerous instances in which fluids are transported from one location to another. The fluids may be gases or liquids and may be at various temperatures and pressures. Additionally, the fluids may be hazardous to man, to his environment or to the equipment used to transport the fluids. Often, especially in the oil and gas industry, it is necessary to transport a fluid from an offshore location, as at a mooring supporting a riser from a subsea wellhead, to a ship (tanker) for transfer to shore. As a ship weathervans about its mooring, it is desirable to accommodate relative rotational movement between elements in a fluid flow path, i.e., that the equipment be able to accommodate changes in orientation between adjacent conduits to minimize or prevent loss of fluid at the junctions in the flow path. In this regard, there is a need for connections that have the capability of relative movement or rotation in order to effectively transfer fluid from one conduit to another. Such connections have typically been referred to as fluid rotary unions (FRUs) or hydraulic utility swivels (HUSs).
In some situations, it is desirable to transport several fluids at a time along multiple conduits and, in certain situations, the fluid flow in at least some of the conduits needs to be bi-directional. Designing an FRU to transport several fluids at a time is generally more difficult than designing an FRU that only carries one fluid at a time. In particular, when fluids are not identical, e.g., the fluids are at different pressures and/or temperatures, the design of an FRU is relatively complex. In such designs, the FRU must accommodate fluids at different pressures and/or temperatures while still allowing for relative rotation between incoming and outgoing conduits and ensuring effective sealing with essentially no cross-contamination between the flowing fluids.
A number of prior art FRUs are disclosed in U.S. Pat. Nos. 4,192,559; 4,296,952; 5,080,401; 5,195,786; 5,538,292; 5,582,432; and 5,669,636, as well as Canadian Patent Nos. 1,161,881 and 1,255,714. Yet another FRU is disclosed in Canadian Patent Application No. 2,236,300. Each of the FRUs found in the foregoing patents or patent applications are generally designed for specific applications and may exhibit sealing problems, especially when utilized to transport fluids at high temperatures and/or pressures or when the fluids are corrosive or hazardous fluids. Further, due to the designs of these prior art FRUs, the FRUs are often difficult to repair or reconfigure.
Another FRU, developed by Focal Technologies, is shown in FIG. 1 and is referred to herein as the model 252 FRU. FRU 10 includes an inner first member or shaft 12 and a concentric outer second member 14, which is rotatable relative to the shaft 12. The shaft 12 includes a flange 16 at one end thereof for direct connection to another section of a pipe line or the like. The shaft 12 has a central axially extending through bore 18 and an annular wall 20, which surrounds the bore 18 over its length and is welded to or integrally formed with the flange 16. A plurality of longitudinally extending internal bores 22 extend along and within the annular wall 20. The bores 22 each have a different length and terminate at a different short radially directed bore 24 that communicates the bore 22 with a cylindrical outer surface 26 of the shaft 12.
The second member 14 is concentric to the shaft 12 and surrounds the shaft 12 over most of its length. Housings 28 and 30 are positioned at opposite ends of the second member 14, each being adapted for secure connection to other structures of a fluid delivery system. The housings 28 and 30 include bearings 32 and 34, respectively, which engage the shaft 12 and permit the relative rotation between the two members.
Extending between the housings 28 and 30 is a cylindrical sleeve member 36, which is securely fixed, as by annular flanges 38 and 40 and machine screws 42 and 44, to the housings 28 and 30, respectively. Positioned within and filling the annular cavity between the sleeve member 36 and the shaft 12 are a plurality of identical longitudinally adjacent annular segments 46. With reference to FIG. 1A, each segment 46 has radially extending face surfaces 48 and 50, a cylindrical outer surface 52 and a cylindrical inner surface 54. Each of the segments 46 includes a circumferentially extending central groove 56 within the inner surface 54 and a smaller cylindrical groove 58 on each side of the groove 56. A single radial bore 60 extends inwardly from the outer surface 52 of the segment 46 and communicates with the groove 56. With reference to FIG. 1D, each of the segments 46 also includes one or more radially directed drain bores 82, each of which extends from the inner surface 54 to a drain port 84 at the outer surface 52. As shown, the segments 46 include an annular groove 66 in the face surface 48 and an annular groove 68 in the other face surface 50. The grooves 66 and 68 are spaced at identical radial distances from the axis of the segment and receive a seal.
The annular segments 46 are positioned within the sleeve member 36 such that the inner surface 54 of each segment is almost in sliding contact with the outer surface 26 of the shaft 12. A circumferential seal element, which may be held by an annular clip, is positioned within each circumferential groove 58 so that the seal element itself makes sealing sliding contact with the outer surface 26. The outer surface 26 of the shaft 12 may be treated with a suitable material, such as tungsten chromium carbide, to reduce wear or galling should the inner surface 54 of one of the segments 46 come into contact with the outer surface 26 of the shaft 12. The segments 46 are positioned within the cavity between the sleeve member 36 and the shaft 12 so that the groove 56 of each segment 46 is in fluid communication with a corresponding one of the radial bores 24 provided at the termination of a bore 22 in the shaft 12 and the seal elements of the segment 46 straddle the fluid connection between the groove 56 and the radial bore 24. As mentioned above, for additional sealing between adjacent ones of the segments 46, the grooves 66 and 68 may be formed in the segments 46 and a circumferential sealing ring positioned therein so as to bridge the gap between adjacent segments at the face surfaces 48 and 50.
The sleeve member 36 has a plurality of circumferentially spaced apertures therethrough at longitudinal positions corresponding generally to the central radial plane of each of the segments 46. (See FIG. 1A). At each such plane, one of the apertures 74 is in fluid communication with the radial bore 60 of the adjacent annular segment located within the sleeve member 36. With reference to FIG. 1C, other apertures 78 contain fasteners 80, which serve to properly locate each of the annular segments 46 in its desired position within the sleeve member 36. The fasteners 80 may include, for example, a hollow plug member 88, which extends from a blind bore 90 in the segment 46 through the aperture 78, and a machine or set screw 92 that passes through the plug 88 and is received in a threaded fashion in blind bore 62.
With the annular segments 46 properly positioned within the sleeve member 36, there is a fluid path established from one of the bores 22 in the shaft 12 to one of the radial bores 24 and then to one of the grooves 56 of one of the segments 46. From the grooves 56, there is fluid communication to the outer surface via the radial bore 60 and to the exterior of the rotary union via a fluid connector that may be in fluid communication with appropriate conduits (not shown) for transporting fluid to other locations. Finally, the drain port 84 may receive a conduit that drains any fluid that may have collected within the region between the shaft 12 and the segments 46. Access to the drain port 84 is provided by way of another aperture 96, which passes through the sleeve member 36. While the above-disclosed FRUs are functional, the above-disclosed FRUs can be relatively expensive to manufacture and difficult to repair.
What is needed is a fluid rotary union (FRU) that substantially maintains the functional benefits of prior art FRUs while providing additional functions with reduced manufacturing costs.